Die assembly for molding of glass element

A die assembly for molding a glass element in a molding apparatus which molds the glass element by placing a glass element material between a pair of upper and lower die assemblies, and heating and pressing the pair of die assemblies and the glass element material, the die assembly comprising:

• an upper core having a peripheral surface, an outside diameter, and an upper molding face for the glass element;
• a lower core having a peripheral surface, an outside diameter, and a lower molding face for the glass element, the outside diameter of the lower core being larger than the outside diameter of the upper core;
• an upper cavity die in which the peripheral surface of the upper core is slidably fit;
• a lower cavity die in which the peripheral surface of the lower core is slidably fit;
• an upper die plate having a lower surface, the upper core and the upper cavity die being connected to the upper die plate;
• a lower die plate that supports the lower core and the lower cavity die at their lower ends
• means for downwardly biasing the upper cavity die, wherein said means presses the lower surface of the upper cavity die against both the upper surface of the lower cavity die and the peripheral portion of the glass element after commencement of die-opening operation when the upper core moves upward together with the upper die plate until a predetermined distance between the upper die plate and the upper cavity die has been reached, thereby forcing the glass element to remain on the lower cavity die side by keeping the position of the glass element;
• and
• a locking section that locks the upper cavity die onto the upper die plate and causes the upper cavity die to move upward together with the upper die plate after the predetermined distance has been reached, the locking section comprising a stopper bolt threadably engaging the upper cavity die and a hole formed in the upper die plate, the hole having a locking step portion on which a head portion of the stopper bolt is to be locked.